Fuel combustion apparatus



Feb. 2, 1960 R. P. FRASER 2,923,348

FUEL COMBUSTION APPARATUS Original Filed Oct. 11, 195] I 4 Sheets-Sheetl mmm'mw mrnmnicn m mmm mwmmw Inventor Raw; P. FRASER Attorney! Feb. 2,1960 R. P. FRASER FUEL COMBUSTION APPARATUS Original Filed Oct. 11, 19514 Sheets-Sheet 2 .OOOOOOOOOO R 8 E m T D' MA MR w m I Feb. 2, 1960 R. P.FRASER 2,923,348

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Attorneys U t States P r o Claims priority, application Great BritainOctober 17, 1950 3 Claims. (Cl. 158-4) This invention relates to theproduction of hot gases for industrial use by the combustion ofrelatively heavyliquid fuel, and to fuel combustion apparatus forproducing such hot gases. The invention has for its chief object theprovision of improved apparatus for the efficient production of cleanhot gaseous currents, such as the production of a clean stream of thegaseous products of combustionof residual fuel oils by the use of oilatomisers. Such hot streams of combustion products and air have variousindustrial uses, as for example the bulk drying of materials and theconcentration of liquors.

This application is a continuation of my application Serial No. 250,890,filed October 11, 1951, now abandoned.

In apparatus for achieving the object of the present invention, thebasic consideration is the completeness or perfection of combustioncombined with a high rate of heat liberation per cubic foot ofcombustion space, and various factors are involved from the practicalaspect, such as controllability of size in relation to known apparatus,and life of the combustion chamber.

The combustion chambers of industrial boilers using fuel oil work at arate of heat liberation of about .05 10 British thermal units per cubicfoot per hour per atmosphere. Furnaces in drying equipment work at about.1 l B.t.u., and marine boilers under forced draught conditions work atup to about 3x10 B.t.u., and all of them have to work with some excessair as otherwise carbon and smoke are produced. These rates might beclassified as a low rate of combustion per cubic foot. On the otherhand, gas turbine combustion chambers work oxygen or an oxidant developstill higher burning in- .tensities.

A specific object of the present invention is the provision of acombustion chamber for industrial use capable of working at anintermediate rate of heat liberation ranging between about 0.5)(10 to3.0x 10 British thermal units per cubic foot per hour per atmosphere,and yet using much less than the usual quantities of excess air or evenusing no excess or a slight deficiency of air.

The combustion of liquid fuels in furnaces and boiler combustionchambers employing normal difiusion flames is always carried out withsome excess air.

The combustion conditions in a boiler using a fuel oil are defined bythe CO content and carbon content of the flue gases and thedetermination of the excess air employed.

A satisfactory excess air figure generally accepted for boiler operationis 45 percent, giving 11 percent CO and about 13 grains of carbon per1,000 cubic feet of exhaust gases (namely Shell Smoke Meter No. The bestoperating practice is represented by 12.5 to 13 percent CO that is tosay 27 percent to 20 percent excess air and no more carbon than theabove figure; namely no visible smoke.

2,923,348 Patented Feb. 2, 196a Just visible smoke is given by carbon inexcess of 22 grains per 1,000 cubic feet.

In the apparatus of the present invention combustion of heavy residualfuel oils can be accomplished at the stoichiometric ratio of fuel to airgiving 15.8 percent CO with a carbon content in the exhaust gases under3 grains per 1,000 cubic feet (Shell Smoke Meter No. 1).

' With distillate fuels the carbon content is nil. This concubic foot,giving a comparatively long life to the refractory of the combustionchamber. The secondary air passing through such combustion chambers isusually controlled by dampers on the combustion plant controlling theflow induced by the main fans on the drying equipment. To burn theheavier residual fuels successfully in such chambers it is essential tocontrol the secondary air for combustion within reasonably close limitsto obtain high flame temperatures. In industrial drying plants this isnot easily accomplished by dampers because the air requirements of thecombustion chamber are not independent of the main fans of the drier.

A further specific object of the present invention, therefore, is toprovide a combustion chamber capable of successfully burning the heavierfuel oils for the production of clean combustion products with completecontrol over secondary combustion air, independent of the variations offlow or pressure of the dilution air required in commercial driers.

In apparatus where the products of combustion are blown directly into aliquor for the purpose of concentrating it, a positive pressure andhigher rate of combustion is required in the combustion chamber. Insuch' apparatus, known as submerged combustion chambers, the source ofheat has usually been gas. In order to burn the heavier fuel oils forthis purpose, it is essential that the combustion should occur at theabove mentioned intermediate rate and be as immaculate as possible sothat no fuel oil or fuel oil vapour passes into the liquor. A stillfurther specific object of the invention is, therefore, to provide amedium high-intensity combustion chamber of small size to allow theheavier residue fuels to be used for the above purpose.

Because the industrial use of hot combustion products is very varied, itis desirable to construct the combustion chamber in such a manner thatits component parts can be renewed in a simple manner from time to time;and

' because the heat output requirement is very varied, this combustionchambershould also be so arranged that the combustion space or volume ofthe chamber can be easily increased within limits by the addition ofunit components without altering the form or manner of assembly of theessential mechanical parts and ancillaries.

For the efiicient atomisation of the heavier liquid fuel oils and theirefi'icient admixture with air, well designed oil atomisers and burnersare necessary and many constructions of oil atomisers and burnerstherefor are known. By means of such atomisers, suitably mounted in abulkhead or furnace end wall and supplied with air for combustion, astream of hot products of combustion can be maintained having as itsorigin a flaming mass of fuel oil particles and air. Such so-calleddiffusion? ism can differ as za eeaa. 9 1s, psnsil lasn Q oal l imtlalcone angle, say 12 to 30, suitable for use in long narrow furnaces, anda flame of wide initial cone angle g v ng a substantially tulip-shapedflame. In such diffus1on flames the surrounding air or atmosphere ofthe. combustion chamber is entrained casually in an uncontrolledturbulent manner towards the axis of the flame. Nevertheless the processis quite rapid. As a result a fuel-rich region lies near the axis of thespray cone, and, regardless of the initial angle of spray, the flameisdrawn out and lengthened. v

In order to achieve the high intensity burning desired, therefore, it isnecessary to provide oxygen in this fuelrlch region. If this were theonly problem, there might well be a simple and obvious solution.However, there is the problem of supplying the fuel in such a dispersedcondition that rapid burning can take place. With gasthe dotted linesare isobars eous type fuels this is also a relatively simple problem,

but with residual fuel oils the problem must be solved by the use of aspecific type fuel atomiser. A third problem, and from a practicalstandpoint perhaps more important problem than the two problems justmentioned, is the problem of insuring a constant aerodynamic pattern toinsure good flame stability over a relatively wide range of, fuelthroughputs. The present invention provides'a solution to all of theseproblems.

According to the present invention, I provide a stationary fuelcombustion apparatus comprising a liquid fuel atomiser in combinationwith a combustion chamber having a front wall and a coaxial rear wall,the said atomiser being mounted axially in the apex region of the frontwall of said chamber and being capable of dispersing into said chamberfinely divided liquid fuel in the form of a widely spread forwardlydivergent cone of spray of at least 45 degrees and preferably 90 or 120degrees or more initial cone-angle, the front wall of the chamber beingcorrespondingly conical and correspondingly wide-spread, and the saidrear wall being of corresponding conicity and size but disposedoppositely and having its apex region formed as an efflux duct, theperipheries of thesaid walls being secured together either directly orby a short cylindrical bridge member, at least one group of circularlydisposed air inlets to the chamber being pro- .vided through the saidrear wall for directing combustion air under pressure converginglytowards the apex region of the cone of fuel spray. By this combinationof features, highly efficient mixing of the fuel particles with the airtakes place by turbulence that is not indiscriminate and uncontrolledbut which on the contrary develops and maintains a constant aerodynamicpattern of circulation which remains steady notwithstanding metering ofthe fuel and air supplies incidental to change of load.

The invention will now be described more fully with reference to theaccompanying drawings which illustrate two embodimentsthereof. In thesedrawings- Figure l is an external side view of one embodiment;

Figure 2 is an end view of the embodiment of Fig. 1;

Figure 3 is an enlarged axial sectional view of the ernbodiment of Fig.1;

Figure 4 is a view of a detail of construction of an igniter used tostart the furnace;

Figure 5 is an external side view of a further embodiment of theinvention;

Figure 6 is a sectional view of a liquid fuel atomising burner suitablefor use in the furnace;

Figure 7 is a diagrammatic representation of the aerodynamic pattern ofthe turbulence in the chamber of Fig. 3;

Figure 8 is a graph of the relation between the be haviour of a chamberaccording to the present invention and the behaviour of known combustionapparatus burning fuel oil, and

Figure 9 is a ap showing sobar o PIHIP e95 around the conical fuel spraywhen issuing from a fuel atomiser of the kind shown in ig. 6. In thisgraph the isobar A of atmospheric pressure-is shown in full lines;

m n M W of subatmospheric pressure. In its simplest aI'th'ugli' ei'ypatriotism, insane combustion chamber of itself comprises two opposedright-angled cone walls connected together at their peripheries, themaximum diameter of the chamber therefore being substantially equalt'oor slightly greater than the distance between the orifice of the fuelatomiser mounted at the apex of the front wall and the centre of theexit in the oppositeor rear Wall.

'Referring first to Figures 1, 2 and 3 which show the apparatus in jitssimplest' form, it is seen that the fuel combustion apparatus comprisesan inner chamberl constituted by the enclosure between two conical walls2 and 3 each of which has about degrees conici'ty, and an outertwo-compartment chamber 4 constituted by the enclosure between theexterior of the two conical chamber walls 2 and 3 and the interior oftwo walls 5 and -6 which form a cylindrical outer shell or casing.

Fuel oil and air enter the chamber 1 with a divergent conical andpreferably vortical motion by projection from a twin-fluid atomiser 7mounted axially of the conical front-wall 2 with its nozzlesubstantially at the apex of the wall. The edge of the front face of theatomiser 7 rests on a narrow seat on the front chamber wall so as tominimisetransfer of heat from the chamber to the atomiser. Fuel oilunder pressure enters the atomiser 7 through the pipe 7a and primary airunder pressure enters through the pipe 712. One embodiment of atomisersuitable for use with this invention will be described hereinafter. Theair pressure conditions that'prevail in and around the fuel spray fromsuch an atomiser and which make it particularly suited to use in mycombustion chamber are illustrated in Figure 9. It is of importance tonotice the isobars of negative pressure in the axial region inside thecone of fuel spray and the consequent strong inducement for air to flowtowards the atomiser into theaxial region of the fuel spray.

The continuation or rear wall 3 of the chamber 1 has its peripheryabutting theperiphery of the front or entry wall 2 and has foi'med inits ana region an efflux duct 8 leading from the combustion chamber 1.'The'two peripheral e dges of the two conical Walls are secured togetherasshown. l

Combustion or secondary air under pressure is supplied through inlet "9'to one of the two compartments of the outer chamber 4. The atomized oiland air spray from the two-fluid atomiser 7 is ignited by'the electricaligniter 10 and the atomiser is designed and adjusted to produce adivergent conical spray following approximately the conical shape of thefront wall 2 of the chamber.

' The main stream of secondary air enters one compartment of the outerchamber 4 from theinlet 9 and then passes into the chamber 1 through twogroups of circularly arranged air inlet passages 11 formed in vthe rearconical wall 3 and is therefore directed inwardly and rearwardly withrespect to the forwardly directed conical fuel spray. The turbulencewithinthechamber 1 is thus of an orderly and controllable character andits aerodynamic flow p at tern isillustrated by the arrowsin Figure 7.

Since the combustion airfrominlets ll is mechanically directed toward,the apex of the conical fuel spray, and since, due to the distributingcharacter of the two-fluid atomiser used, thepressure near .the' apex ofand within the cone of vertically whirling air and fuel spray isrelatively low as hereinbefor e explained with reference to Fig. 9, thecombustion air directedthrough the inlets in the rear conical wall ofthe combustion chamber is strong- 1y induced .to how towards the .saidapex, the stability of the aerodynamic flow pattern of the turbulence,and the stability of the ignition point of the atomised fuel and airmixtu e, is extremely high.

. Another separately controlled .part of .the total air for combustion:flOWS .to at least one .group of circularly disposed inlets through thefront conical wall'of the chamber.

The air jets from these latter inlets impinge on them;-

temal surface of the conical fuel spray and to some extent mix with itand to some extent penetrate it but are not such as to annul theoppositely directed jets. By this method of injecting the combustion airto cause internal circulation towards the fuel spray apex to causeintense fuel and air mixing and more than usually rapid combustionwithin the fuel spray cone, the fuel burns as a wideangled compactturbulent flame within the chamber to a condition of completeness ofcombustion controllable exactly by the proportions of fuel and air.

This part of the secondary air may enter the chamber 1 as shown by wayof the air inlet 9 and the other compartment of the outer chamber 4 andthrough the group of circularly disposed inlet passages 12 formed in thefront or entry wall 2 of the chamber 1, so that the aerodynamic flowpattern of the controlled turbulence is that illustrated by the arrowsin Figure 7.

A part of the air from inlet 9 passes through a branch pipe 13 (Figure2) to an inlet connection 14 (Figure 3) on the housing of the igniter soas to circulate around the igniter (before escaping into the chamber 1)thereby keeping the igniter body cool. The igniter is withdrawable intoits housing so that its tip does not remain exposed to the direct heatof the chamber after ignition has been efiected.

Another part of the air from the inlet 9 passes through a branch pipe 15to circulate similarly around and through an inspection tube 10' mountedsimilarly to the igniter 10. A small controlled portion of the airentering the chamber 1 passes through passages 16 (Figure 3) and isthereby directed on to the rear surface of the atomised oil and airspray from the atomiser 7.

The air passing from the outer chamber 4 to the combustion chamber 1 byway of the inlet passages 11 and 12 is guided by inlet directing plates17 forming pockets over said inlet passages.

For many purposes the combustion chamber 1 is advantageously of the formconstituted by two conical walls connected face to face as shown inFigure 3. -If the chamber is constructed with two opposed right circularcones, then the maximum diameter of the chamber is equal to its length.If a chamber of larger volume but of the same diameter is desired thismay readily be obtained without materially impairing the aerodynamicpattern of turbulence by introducing a cylindrical component between thetwo conical walls as shown at 18 in Figure 5, provided that the lengthof the cylindrical component is not greater than the height of one ofthe cone walls. If the space enclosed by two opposed right circularcones is considered as unit volume then an increase of length of thechamber by 50 percent by the addition of a cylindrical portion betweenthe cones, increases the volume 2.5 times. Thus considerable changes ofcombustion chamber volume are possible without any great change in thegeneral form of the chamber or in the aerodynamic pattern of theturbulence within it and without any change whatever in the end coneunits carrying respectively the atomiser and the efflux duct.

It Will be understood that the temperature inside the combustion chamber1 is high and that the combustion chamber wall may therefore be linedwith refractory material 19 as shown, asbestos composition also beingused as packing 20 atthe junction of the wall components.

It will also be understood that heat passing through the walls of thecombustion chamber 1 will preheat the secondary air in the compartmentsof the outer chamber 4. On the other hand the incoming cold secondaryair in these compartments helps to keep down the temperatfire of therefractory walls of the combustion chamber.

The secondary air or gas supply passages 11 and 12 extending through therefractory lined Walls of the combustion chamber may be constituted byrefractory lined steel tubes or by refractory tubes, and such tubes,with or without nozzles, may be arranged in a circular row or in two ormore such rows as shown, the tube axes intersecting on the longitudinalaxis of the chamber or being set at a small inclination preferably suchthat the injected air streams augment any rotational component in thefiame gases.

The liquid fuel atomiser employed may be of the simple pressure type,namely a single orifice swirl-spray pressure nozzle producing a conicalsheet of liquid fuel which becomes a conical spray of fuel particleshaving the desired spray angle, or it may be and preferably is of thetwin-fluid or blast type using air or steam as an atomising medium, inwhich case the said medium supplied under pressure to the interior ofthe atomiser assists in atomising and spreading the liquid fuel as aWideangled cone of spray of admixed fuel particles and atomising medium.When using a twin-fluid atomiser with air as the atomising medium theatomising air also serves as combustion air and may be termed primaryair and may comprise up to 10 percent of the total combustion airrequired; but at least 40 percent of the total air required forcombustion is supplied through the rear conical wall of the chamber. Oneform of preferred twinfiuid atomiser capable of producing a high degreeof vortical motion in the fuel spray and relatively low pressureconditions near the fuel cone apex inside the cone serving to furtheraid the axial circulation towards the apex of the fuel cone spray ishereinafter described.

The oil atomiser, as shown in Figure 6, comprises a tubular outer bodyor shell 21 with terminal cap 22, and an inner hollow body member 23having an externally dish-shaped head piece 24 co-operating at itsperiphery with an internally conical lip 25 on the forward end of thecap 22 to form a gap 26 of predetermined size so that air or steamsupplied to the shell at its rear end will emerge as a conicallyconverging stream from the said gap 26. Inclined vanes 27 on thecylindrical Wall of the hollow body member 23 serve to impart a swirlingmotion to the stream of air or steam before it reaches the said gap.

Inside the front end of the hollow body member 23' is fitted a liquidspray forming member 28. The spray forming member 28 is externallyhemispherical at its forward end to seat against a conical formation 29behind the dish-shaped head piece 24. The said spray member is hollowwith an exit orifice 30 in register with a central opening 31 in thehead piece 24, and said spray member is formed with tangentially cutinlet slots 32 in its skirt portion which is seated on a tubular stem orplug 33, so that liquid fuel entering the interior of the said bodyportion will be whirled before escaping from the orifice 30. Liquid fuelreaches the inlet slots 32 of the spray forming member 28 from a supplypipe 34 connected axially to the base of the hollow body member. Fromthe pipe 34 the liquid fuel passes into the interior of the body members23 and along the interior of the aforesaid stem 33 at the rear of thespray member 28 and out through radial holes 35 into the annular space36 existing between the forward end of the hollow body member 23 and thespray member 28 and thence to the said inlet slots 32. It will thereforebe understood that the liquid fuel emerges from the exit orifice 30 andopening 31, while whirling air or steam emerges convergingly from theannular gap 26.

Assuming that the atomiser 7 is supplied with fuel oil? at a pressure offrom 1-100 pounds per square inch and with primary air for atomisingpurposes at a pressure of 3-20 pounds per square inch (these pressuresdepend ing on the design of atomiser used), the secondary com bustionair introduced through the tubes or nozzles in? the wall of thecombustion chamber 1 may be supplied at a pressure of say one to fivepounds per square inch (above atmospheric pressure), in which case asteady stream of combustion products and air can be arranged-i to flowthrough the chamber outlet or efflux duct 8 at as, pressure of about say0.1 to 2.0 pounds per square inch.

(above'atmosphericpressure). Effective turbulence in the chamber 1 canbe obtained with a pressure drop across the tubes 11 and 12 varying from0.4 to 5 pounds per square inch, as for example with a pressure dropfrom 0.5 to 0.1 pound per square inch, or from 5 pounds to 3.5 pounds,or from pounds to 8 pounds, or from 20 pounds to 19 pounds, or from 50'pounds to 45 pounds.

Generally speaking the combustion air or a substantial proportion of thecombustion air employed in carrying out the present invention has a flowcomponent contra to the forwardly divergent cone of fuel spray so thatit is projected to the region inside the said cone of spray. This highproportion of air within the spray cone causes the combustion to takeplace within the said cone, and notonly externally on a narrow cone asin the usual diffusion flame.

As will be readily understood a hot gaseous stream of such a characterhas many industrial uses. When applied to apparatus for dryingmaterials, the hot products issuing from the apparatus will be passedinto a duct and mixed with further air to reduce the temperature. It isusual in such drying apparatus to employ suction fans to draw the hotair over or through the product, and an important feature and advantageof the apparatus above described is that it is substantially insensitiveor indifferent to fluctuations of gaseous pressure that may occur beyondits delivery outlet due to varying conditions of industrial use of thestream at a point remote from the apparatus. Therefore, notwithstandingsuch varying conditions and varying requirements of industrial use ofthe delivered stream, the supplier of the apparatus can meet any supplyrequirements solely or mainly by consideration merely of the performanceof his own apparatus. That is to say the quantity of secondarycombustion air flowing through the combustion chamber can be arranged sothat it is independent of changes of suction due to the fan on thedryer.

A further feature and advantage of the apparatus is that it is capableof burning efficiently furnace oils of high viscosity and that theproducts of combustion are clean. It has been found that with theapparatus according to the invention the heaviest fuel oils (3,000 secs.Redwood No. 1 at 100 F.) can be burned under conditions of completecontrol with either excess air or at theoretical proportions, or with aslight deficiency of air without the formation of carbon or smoke. causeof the particular aerodynamic flow pattern created in the chamber asshown in Figure 7, the stabilisation of any particular degree ofcombustion is so good that the operator can make extremely rapid orinstantaneous changes from combustion occurring with above thestoichiometric quantity of air to combustion occurring with slightlyless than the stoichiometric quantity of air. As will be readilyunderstood, the apparatus is extremely simple in construction and iscomposed of only a few, readily assembled components and is easilyconvertible. in capacity by addition of a simple component ofconstruction.

A further surprising and unexpected feature of the apparatus is that itmay be started instantaneously at full load when the combsution chamberis cold.

In illustration of the surprising results obtainable by the presentinvention it may be stated that the heat release rates using fuel oil inan ordinary domestic sectional boiler and in a combustion chamberaccording to the present invention are 0.()4 10 British thermal unitsper cubic foot per atmosphere and 1.0 to 3.() 10 re spectively (seetransactions of the Institution of Chemical Engineers, London, vol. 35,No. 3, 1957 (page 224); also Proceedings of the Joint Conference onCombustion of the Institution of- Mechanical Engineers (London), and TheAmerican Society of Mechanical Engineers Discussion in London onIndustrial Furnaces (pages 220-, 2

Further, be-' It is to be noted, therefore, that the heatre-v lease ratein a combustion chamber according to the 8 present inventionissurprisingly high, namely, from 25 to 75 times as high as in anordinary domestic boiler.

It is believed that these results can be attributed to the manner inwhich the apparatus solves the particular problems involved in the highintensity burning of heavy residual fuels. The supplying of air to thefuel-rich region in the centre of the spray cone is carried out byinjecting a large portion of the secondary air into the centre of thespray cone in a direction contra to the spray cone. When additionalsecondary air is also injected through the front Wall of the combustionchamber, this results in secondary air being applied to both sides ofthe spray cone, thus promoting an extremely high mixing and burningrate. The specific type of atomiser is also important, for it aids insolving two of the important problems. First it produces an extremelysmall particle size having an extremely short burning time. Thispromotes high intensity of burning and a resulting high rate of heatliberation. Perhaps more important, however, the atomiser produces awhirling conical spray at a constant spray angle at all fuel throughputs. The high rotary component of velocity producing the whirling keepsthe spray cone stable and at the same time produces the lower pressureinside the vortex of whirling spray which aids the flow of secondary airinto the spray cone as already described with reference to Figure 9.This stable spray cone together with the shape of the chamber whichcorresponds to the shape of the spray cone produces the stableaerodynamic pattern essential to the stability of the flame.

With this stability, high intensity combustion can be maintained byvolumetric metering of the flow of fuel and air at various fuelthroughputs.

Combustion apparatus as above described enables the combustion of liquidfuel to take place under such surprisingly good control that a stream ofclean hot gases substantially free from carbon particles or smoke andconsisting of carbon dioxide and nitrogen, but substantially no oxygenor only alinn'ted and known constant quantity, can be maintained.Combustion using substantially the stoichiometric quantity of combustionair is in fact achieved which approximates theoretical perfection. Suchhot clean gases can be put to a variety of industrial uses. Even whenoperating with a heavy fuel and with a fuel to air ratio somewhat richerthan stoichiometric, hot gases containing no smoke can still beproduced.

A graphic comparison between the performance of the combustion apparatusof the present invention and that of other combustion chambers isillustrated in Fig. 8 where the line AB is what is known in the art as abest practice envelope, this being-a line drawn between the rates ofburning of different apparatus compared with the secondary air pressuredrop used in them. The highest point B of the line AB is represented bythe so-called ideal combustion reactor" having near ideal mixingv ofvaporised octane, and the point A being the lowest or ordinary type ofcombustion equipment utilizing a low pressure difference. Apparatus ofgood design should lie as close to the line of the ideal envelope AB aspos sible, and the opposed cone chamber of the present invention isindicated on this figure by the line CD. This. line CD is seen to beclose and nearly parallel to the line AB.

From the extremely practical viewpoint of costs and suitability of theapparatus in its installation, the cost of running the auxiliaryequipment necessary to give the fuel and air the necessary momentum ishigher than with conventional low intensity equipment, but the capitalcost of the apparatus is much less due to the small amount of materialused in the combustion device itself. Moreover, because of therelativelysmall size, the ap paratus may be moreconveniently installed in agreater variety of locations, and its over-all cost iseven further edued. au l t t e mall pla pace. qs up st The overall apparatus isextremely cool in operation, being able to run with an outer shelltemperature as low as 40 0., thus reducing the ventilating problems inthe area surrounding the apparatus as well as increasing its over-allefiiciency. From the standpoint of noise, an ever increasing industrialproblem, when the apparatus is used at modest pressure drops of from 1to 5 pounds, it is so quiet in its operation that in many cases it isnecessary to provide visual means to indicate that the flame is lit.

I claim:

1. A stationary combustion apparatus for burning liquid fuel to producea stream of hot clean gases at a rate of heat liberation ranging from0.5 to 3.0)(10 British thermal units per cubic foot per hour peratmosphere, said apparatus comprising a liquid fuel atomiser incombination with a combustion chamber having a front wall and a coaxialrear wall, the said atomiser being mounted axially in the apex region ofthe front wall of said chamber and being capable of dispersing into saidchamber finely divided liquid fuel in the form of a Widely spreadforwardly divergent whirling cone of spray of at least 90 degrees coneangle, the front wall of the chamber being correspondingly conical andcorrespondingly wide-spread, and the said rear wall being ofcorresponding conicity and size but disposed oppositely and having itsapex region formed as an efliux duct, the peripheries of the said wallsbeing secured directly to one another, at least one group of circularlydisposed air inlets to said chamber being provided through the said rearwall for directing combustion air under pressure convergingly towardsthe relatively low pressure apex region of the cone of fuel spray,whereby a steady aerodynamic pattern of turbulence and mixing ismaintained Within the chamber, said apparatus also having at least onegroup of circularly disposed air inlets through said front Wall fordirecting separately controlled combustion air under pressure to impingeon the external surface of the fuel cone spray, and a casing around saidconical walls and spaced therefrom and forming an outer chamber aroundeach conical wall of the combustion chamber for the supply of separateand separately controllable combustion air to the inlets through thesaid walls, whereby the combustion air is preheated within said outerchambers, and the conical walls of the combustion chamber arecorrespondingly cooled.

2. A stationary combustion apparatus for burning liquid fuel to producea stream of hot clean gases at a rate of heat liberation ranging from0.5x 10 to 3.0)(10 British thermal units per cubic foot per hour peratmosphere, said apparatus comprising a liquid fuel atomiser incombination with a combustion chamber having a front wall and a coaxialrear wall, the said atomiser being mounted axially in the apex region ofthe front wall of said chamber and being capable of dispersing into saidchamber finely divided liquid fuel in the form of a widely spreadforwardly divergent whirling cone of spray of at least 45 degrees coneangle, the front wall of the chamber being correspondingly conical andcorrespondingly wide-spread, and the said rear wall being ofcorresponding conicity and size but disposed oppositely and having itsapex region formed as an efilux duct, the peripheries of the said wallsbeing secured directly to one another, at least one group of circularlydisposed air inlets to said chamber being provided through the said rearwall for directing combustion air under pressure convergingly towardsthe relatively low pressure apex region of the cone of fuel spray,whereby a steady aerodynamic pattern of turbulence and mixing ismaintained within the chamber, said apparatus also having at least onegroup of circularly disposed air inlets through said front wall fordirecting separately controlled combustion air under pressure to impingeon the external surface of the fuel cone spray, and a casing around saidconical walls and spaced therefrom and forming an outer chamber aroundeach conical wall of the combustion chamber for the supply of separateand separately controllable combustion air to the inlets through thesaid walls, whereby the combustion air is preheated within said outerchambers, and the conical walls of the combustion chamber arecorrespondingly cooled.

3. Stationary combustion apparatus as claimed in claim 2 and acylindrical bridge member of length not more than the height of oneconical wall of the said chamber connecting the peripheries of theopposed front and rear cone walls of the combustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS2,367,119 Hess Jan. 9, 1945 2,536,599 Goddard Jan. 2, 1951 2,541,171McGarry Feb. 13, 1951 2,601,000 Nerad June 17, 1952 2,603,064 WilliamsJuly 15, 1952 2,638,895 Swindin May 19, 1953 2,712,351 Roth July 5, 1955FOREIGN PATENTS 376,570 Germany May 30, 1923

